2009 Jupiter impact event explained

Place:	Jupiter

The 2009 Jupiter impact event, occasionally referred to as the Wesley impact, was a July 2009 impact event on Jupiter that caused a black spot in the planet's atmosphere. The impact area covered 190 million square kilometers, similar in area to the planet's Little Red Spot and approximately the size of the Pacific Ocean.^[1] The impactor is estimated to have been about 200 to 500 meters in diameter. (For comparison, the one for the Tunguska event was estimated to be in the 60–190 meters range.)

Discovery

Amateur astronomer Anthony Wesley discovered the impact at approximately 13:30 UTC on 19 July 2009 (exactly 15 years after the Jupiter impacts of comet Shoemaker–Levy 9, or SL9). He was at his home observatory just outside Murrumbateman, New South Wales, Australia, using stacked images on a 14.5adj=onNaNadj=on diameter reflecting telescope equipped with a low light machine vision video camera attached to the telescope.^[2] Wesley stated that:

Wesley sent an e-mail to others including the NASA Jet Propulsion Laboratory in Pasadena, California reporting his observations.^[3]

Findings

Paul Kalas and collaborators confirmed the sighting. They had time on the Keck II telescope in Hawaii, and had been planning to observe Fomalhaut b, but they spent some of their time looking at the Jupiter impact.^[4] Infrared observation by Keck and the NASA Infrared Telescope Facility (IRTF)^[1] at Mauna Kea showed a bright spot where the impact took place, indicating the impact warmed a 190 million square km area of the lower atmosphere at 305° west, 57° south near Jupiter's south pole.^[1]

The spot's prominence indicated that it was composed of high-altitude aerosols similar to those seen during the SL9 impact.^[4] Using near-infrared wavelengths and the IRTF, Glenn Orton and his team detected bright upwelling particles in the planet's upper atmosphere and using mid-infrared wavelengths, found possible extra emission of ammonia gas.^[5]

The force of the explosion on Jupiter was thousands of times more powerful than the suspected comet or asteroid that exploded over the Tunguska River Valley in Siberia in June 1908.^[6] (This would be approximately 12,500–13,000 megatons of TNT, over a million times more powerful than the bomb dropped on Hiroshima).^[7]

Impactor

The object that hit Jupiter was not identified before Wesley discovered the impact. A 2003 paper estimated comets with a diameter larger than 1.5 kilometers impact Jupiter about every 90 to 500 years,^[8] while a 1997 survey suggested that the astronomer Cassini may have recorded an impact in 1690.^[9]

Given the size of the SL9 impactors,^[10] it is likely that this object was less than one kilometer in diameter.^{[6] [11]} Finding water at the site would indicate that the impactor was a comet,^[12] as opposed to an asteroid or a very small, icy moon.^[13] At first it was believed that the object was more likely to be a comet since comets generally have more planet-crossing orbits.^[14] At the distance of Jupiter (5.2 AU) most small comets are not close enough to the Sun to be very active, and so would be hard to detect.^[14] Small kilometer-sized asteroids would also be hard to detect, however, and recent work by Orton et al. and Hammel et al. has strongly suggested the impactor was an asteroid, as it left only one impact site, did not reduce Jovian decametric radiation emission by contributing significant dust to the Jovian magnetosphere, and produced high altitude dusty debris full of silica, very different than what was produced by SL9.

As of 2012, the impactor is believed to have been an asteroid with a diameter of about 200 to 500 meters.^[15]

Visibility

Assuming it was an inactive comet (or asteroid) about 1 km in diameter, this object would have been no brighter than about apparent magnitude 25.^[14] (Jupiter shines about 130 billion times brighter than a 25th magnitude object.)^[16] Most asteroid surveys that use a wide field of view do not see fainter than about magnitude 22 (which is 16x brighter than magnitude 25).^[14] Even detecting satellites less than 10 km in diameter orbiting Jupiter is difficult and requires some of the best telescopes in the world.^[17] It is only since 1999 with the discovery of Callirrhoe that astronomers have been able to discover many of Jupiter's smallest moons.^[18]

See also

• Impact events on Jupiter
• List of Jupiter events

Further reading

• Hammel . H. B. . Wong . M. H. . Clarke . J. T. . De Pater . I. . Fletcher . L. N. . Hueso . R. . Noll . K. . Orton . G. S. . Pérez-Hoyos . S. . Sánchez-Lavega . A. . Simon-Miller . A. A. . Yanamandra-Fisher . P. A. . 10.1088/2041-8205/715/2/L150 . Jupiter After the 2009 Impact:hubble Space Telescopeimaging of the Impact-Generated Debris and Its Temporal Evolution . The Astrophysical Journal . 715 . 2 . L150 . 2010 . 2010ApJ...715L.150H . free . .
• Sánchez-Lavega . A. . Wesley . A. . Orton . G. . Hueso . R. . Perez-Hoyos . S. . Fletcher . L. N. . Yanamandra-Fisher . P. . Legarreta . J. . De Pater . I. . Hammel . H. . Simon-Miller . A. . Gomez-Forrellad . J. M. . Ortiz . J. L. . García-Melendo . E. . Puetter . R. C. . Chodas . P. . The Impact of a Large Object on Jupiter in 2009 July . 10.1088/2041-8205/715/2/L155 . The Astrophysical Journal . 715 . 2 . L155 . 2010 . 1005.2312 . 2010ApJ...715L.155S . 119251280 . .

External links

• Web site: Photo of Anthony Wesley and his telescope. (jupiter.samba.org). 2009-07-21. https://web.archive.org/web/20090726100856/http://jupiter.samba.org/AnthonyWesley.jpg. 26 July 2009 . live.
• Jupiter Section of ALPO-Japan with Latest Jupiter Observations
• Aussie stargazer spots scar from Jupiter collision
• A comet or meteoroid hits Jupiter
• Jupiter - friend or foe? (arXiv:0806.2795)
• APOD 9/8/2009, Unexpected Impact on Jupiter polar projection animation
• Simulations unravel mysteries of 2009 Jupiter impact (physorg.com March 30, 2012)

Notes and References

1. http://www.berkeley.edu/news/media/releases/2009/07/21_bruise.shtml Jupiter pummeled, leaving bruise the size of the Pacific Ocean
2. News: Mackey, Robert. Amateur Finds New Earth-Sized Blot on Jupiter. July 21, 2009. The New York Times. 2009-07-21.
3. News: O'Loughlin, Toni and agencies. Amateur astronomer spots Earth-size scar on Jupiter. The Guardian. 2009-07-21 . London . 2009-07-21. https://web.archive.org/web/20090729221115/http://www.guardian.co.uk/science/2009/jul/21/jupiter-scar-comet-asteroid-crash. 29 July 2009 . live.
4. http://keckobservatory.org/index.php/news/jupiters_adds_a_feature/ Jupiter adds a feature
5. Web site: Martinez, Carolina. New NASA Images Indicate Object Hits Jupiter. July 20, 2009. Jet Propulsion Laboratory. 2009-07-21. https://web.archive.org/web/20090727121804/http://www.nasa.gov/topics/solarsystem/features/jup-20090720.html. 27 July 2009 . live.
6. Web site: Hubble Captures Rare Jupiter Collision . Hubblesite (STScI-2009-23) . 2009-07-24 . 2009-07-24.
7. Book: Longo, Giuseppe . 18: The Tunguska event . Bobrowsky . Peter T. . Rickman . Hans . Comet/Asteroid Impacts and Human Society, An Interdisciplinary Approach . 303–330 . Springer-Verlag . Berlin Heidelberg New York . 2007 . http://www-th.bo.infn.it/tunguska/Asteroids-Chapter-18.pdf . 978-3-540-32709-7 . 2007 . 2009-07-26 . 2009-07-29 . https://www.webcitation.org/5icderdjK?url=http://www-th.bo.infn.it/tunguska/Asteroids-Chapter-18.pdf . bot: unknown . . Accessed 2009-07-27. 2009-07-29.
8. Kevin . Zahnle . Paul . Schenk . Harold . Levison . Luke . Dones . 2003 . Cratering rates in the outer Solar System . . 163 . 2 . 263–289 . 2003Icar..163..263Z . 1.5-km-diameter comets is currently N(d > 1.5 km) = 0.005 per annum . https://www.webcitation.org/5icdGOsFF?url=http://lasp.colorado.edu/~espoclass/homework/5830_2008_homework/Zahnle2003CrateringRates.pdf . 2009-07-29 . 2009-07-27 . 10.1016/S0019-1035(03)00048-4 . 10.1.1.520.2964 .
9. Isshi . Tabe . Jun-ichi . Watanabe . Michiwo . Jimbo . February 1997 . Discovery of a Possible Impact SPOT on Jupiter Recorded in 1690 . Publications of the Astronomical Society of Japan . 49 . L1–L5 . 1997PASJ...49L...1T . Jupiter has been continuously monitored for almost 400 yr . 10.1093/pasj/49.1.l1. free .
10. Web site: Comet Shoemaker-Levy 9 Fragment Size . Lunar and Planetary Institute . D. A. Crawford . 2009-07-22.
11. Web site: Surprise Collision on Jupiter Captured by Gemini Telescope . 23 July 2009 . Gemini Observatory . 2009-07-24.
12. Perlman, David. "Glowing scar is revealing Jupiter's secrets" San Francisco Chronicle, 23 July 2009.
13. News: Jupiter sports new 'bruise' from impact . Grossman. Lisa. 2009-07-21. New Scientist. 2009-07-22. https://web.archive.org/web/20090803010347/http://www.newscientist.com/article/dn17491-jupiter-sports-new-bruise-from-impact.html. 3 August 2009 . live.
14. Web site: More on the Jupiter Impact . Carl Hergenrother . Blog . The Transient Sky . 2009-07-21 . 2009-07-24.
15. Web site: January 26, 2011 . Asteroids Ahoy! Jupiter Scar Likely from Rocky Body . News and Features @ NASA/JPL . Jia-Rui C. Cook . 2011-01-26. https://web.archive.org/web/20110127202427/http://www.jpl.nasa.gov/news/news.cfm?release=2011-028. 27 January 2011 . live.
16. (\sqrt[ 5 ]{ 100 }) ^{25-(-2.8)} =131 billion (1.3)
17. Web site: New Satellites of Jupiter Discovered in 2003 . Carnegie Institution (Department of Terrestrial Magnetism) . Scott S. Sheppard . Scott S. Sheppard . 2009-07-23. https://web.archive.org/web/20090608233946/http://www.dtm.ciw.edu/users/sheppard/satellites/jup2003.html. 8 June 2009 . live.
18. Web site: New moon of Jupiter found . SpaceFlight Now (University of Arizona News Release) . 2009-07-23.